i would like to know more about how to drill out the exhaust,did you put a k&n in too!still would like to know if anyone can to me how to get to the fly wheel,do i take the whole left side of the case off.i got ignition advance key from curtice sparks that i would like to know how ,or anyone has done it before if the could help methanks in advance.

 

The fly wheel as you refer to it is the magneto and yes it is under the left side case. Just remove the cover and there it is. You will have to use a flywheel pulling tool to remove it once you get it of the shaft just remove the old key and install the new one and them reinstall the flywheel. To get the flywheel off make sure you use the right tool they make a puller used just for taking the flywheel off of the 400ex you do not want to damage the fly wheel.